As we age, maintaining muscle mass and strength becomes increasingly important for overall health, mobility, and quality of life. Resistance training has long been the gold standard for counteracting age-related muscle loss, but recent studies are shedding light on how different types of resistance training may yield unique adaptations. One of the most compelling distinctions is between eccentric (muscle-lengthening) and conventional (both muscle-lengthening and muscle-shortening) resistance training. In this article, we explore a 2009 study by Reeves et al., which highlights the distinct benefits that eccentric-only training can offer older adults compared to conventional methods.
Study Overview
The study, conducted by Reeves et al., investigated how eccentric-only resistance training (focusing exclusively on muscle-lengthening contractions) compares to conventional resistance training, which includes both concentric (muscle-shortening) and eccentric phases. The research involved older adults, with one group performing eccentric-only exercises and another engaging in conventional resistance training. Both groups trained three times per week for 14 weeks, using leg press and knee extension exercises at 80% of their five-repetition maximum (5RM).
The goal of the study was to determine whether training with eccentric contractions, which allow for higher loads, would lead to superior muscle structure and strength adaptations compared to conventional resistance training.
Key Findings
1. Fascicle Length and Pennation Angle
- Eccentric Training: The eccentric group experienced a 20% increase in fascicle length (the length of muscle fibers) compared to an 8% increase in the conventional group.
- Conventional Training: The conventional group saw a 35% increase in pennation angle (the angle at which muscle fibers insert into the tendon), while the eccentric group only experienced a 5% increase.
Interpretation:
These differences suggest that eccentric training promotes the addition of sarcomeres in series (lengthening muscle fibers), whereas conventional training encourages sarcomeres to grow in parallel (increasing muscle thickness). The difference in muscle architecture may influence how each training method impacts muscle function.
2. Muscle Thickness
Both groups saw similar increases in muscle thickness, with approximately 12% growth in muscle size.
Implication:
Although muscle size increased to a similar extent in both groups, the changes in architecture (fascicle length vs. pennation angle) imply that the functional outcomes could vary. Eccentric training may improve a muscle’s ability to generate force across a longer range of motion, while conventional training could enhance the muscle’s ability to produce force at shorter lengths.
3. Strength Adaptations
- Eccentric Group: The eccentric training group saw 9-17% increases in eccentric knee extensor torque (strength) across a range of angular velocities, but no significant gains in concentric strength.
- Conventional Group: The conventional group experienced 22-37% increases in concentric torque, but no significant changes in eccentric torque.
Takeaway:
The study reinforces the principle of specificity in strength training: strength gains are specific to the type of contraction used during training. The eccentric group improved their ability to resist lengthening forces, while the conventional group enhanced their ability to produce force during muscle shortening.
4. Perceived Effort (RPE)
Despite using heavier loads, the eccentric group reported a significantly lower rating of perceived exertion (RPE) than the conventional group. On a scale from 6 to 20, the eccentric group averaged an RPE of 13.7, compared to 15.7 in the conventional group.
Significance:
Eccentric training may be more tolerable for older adults due to the lower perceived effort, making it an appealing option for those looking to maintain or improve muscle mass with less fatigue or strain.
Practical Applications for Older Adults
Given the findings, eccentric-only resistance training offers some unique advantages, particularly for older adults. These benefits include:
- Improved muscle architecture: The increase in fascicle length from eccentric training suggests greater potential for improving range of motion and overall functional strength.
- High loads with lower effort: Eccentric training allows older adults to train with higher loads without feeling as fatigued. This may enhance adherence to training programs, a critical factor in long-term health outcomes.
- Targeted strength gains: Eccentric training can be used to specifically enhance eccentric strength, which is important for activities that involve controlling or resisting force, such as walking downhill or lowering objects.
Comparison with Other Studies
The results of the Reeves et al. study align with several other investigations into the benefits of eccentric training:
- Hortobágyi et al. (2001): This study found that eccentric training results in greater eccentric strength gains than concentric-focused training, similar to the findings in the older adults studied by Reeves et al. This reinforces the idea that training adaptations are contraction-specific.
- Blazevich et al. (2007): Research into muscle architecture changes with eccentric training shows that fascicle length increases are more pronounced in response to eccentric loads. This may lead to improved muscle function and reduced risk of injury.
- Higbie et al. (1996): Young adults who underwent eccentric-only training saw significant strength gains specific to the type of contractions they performed, again highlighting the principle of specificity.
Recommendations for Training Older Adults
For older lifters and those designing resistance training programs for this population, it is essential to consider the specific benefits of eccentric training. Here are a few practical recommendations:
- Include Eccentric Movements: Eccentric-only exercises or slow, controlled eccentric phases in conventional exercises can be integrated into resistance training programs to maximize strength gains while minimizing fatigue.
- Focus on Progressive Overload: Given the potential for eccentric training to tolerate higher loads, gradually increasing the resistance during the eccentric phase can stimulate greater muscle growth and adaptation.
- Alternating Training Modes: To capitalize on both the concentric and eccentric strength gains, alternating between eccentric-focused and conventional resistance training cycles may provide a more comprehensive approach to muscle development in older adults.
Conclusion
The study by Reeves et al. demonstrates that eccentric and conventional resistance training yield different adaptations in muscle strength and architecture. Eccentric training appears to offer unique benefits for older adults, including greater fascicle length increases and a lower perceived effort, making it a valuable tool for maintaining muscle function and strength in later years. By incorporating eccentric movements into training programs, older lifters can maximize their potential for muscle growth and overall functional fitness.
References
Reeves, N.D., Maganaris, C.N., Longo, S., Narici, M.V. (2009). Differential adaptations to eccentric versus conventional resistance training in older humans. Experimental Physiology.
Blazevich, A.J., et al. (2007). Muscle architectural adaptations to eccentric loading. Scandinavian Journal of Medicine & Science in Sports.
Hortobágyi, T., et al. (2001). Greater eccentric versus concentric strength gains after training with a dynamometer. Journal of Aging and Physical Activity.
Higbie, E.J., et al. (1996). Effects of eccentric and concentric training on muscle strength. Journal of Strength and Conditioning Research.
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